function push(array, ...items) {
    array.push(...items);
  }
  
  function add(x, y) {
    return x + y;
  }
  
  const numbers = [4, 38];
  add(...numbers) // 42

  function f(v, w, x, y, z) { }
const args = [0, 1];
f(-1, ...args, 2, ...[3]);
let x = 3;
const arr = [
    ...(x > 0 ? ['a'] : []),
    'b',
  ];
  console.log(arr)